Piston engine provided with control valve



Jan. 19, 1960 H. HERRMANN PISTON ENGINE PROVIDED wrm CONTROL VALVE FiledSept. 26. 1958 IN VEN TOP ,W M MW 5 f H a T W HB/ W 6 however alsodepends on the frequency.

United States Patent Ofihce 2,921,559 Patented Jan. 19, 1960 PISTONENGINE PROVIDED WITH CONTROL VALVE Helmnt Hermann, Altlunen, Germany,assignor to Gewerkschaft Elsenhutte Westfalia, Wethmar, bei Lunen,Westphalia, Germany, a corporation of Germany Application September 26,1958, Serial No. 763,538

Claims priority, application Germany October 8, 1957 Claims. (Cl.121-16) This invention relates to piston engines such as, for example,are employed to impart vibration to vibrating apparatus. Moreparticularly, the invention relates to the manner in which motivemedium, such as air, is supplied to such engines.

In the case of free piston engines which serve f instance as drives forvibrating machines and in connection with which elastic interception ofthe piston is effected by air buffers, it is not possible to make thecontrol of the operating air positively dependent upon the pistonmovement. This is due to the fact that the engine housing effectsdifferent strokes with respect to the piston, depending on the load. Ifthe engine for instance is installed on a vibrating apparatus, then asis known, the one swinging mass is the piston and the second the enginehousing, with the moving parts of the vibrating device. The mass of thepiston, however, is as a rule very much less than the rest of the mass.As long as no work is given off toward the outside by the vibratingapparatus, the two masses swing about their common center of gravity. Ifhowever work is given off, then the common center of gravity isdisplaced. This displacement of the center of gravity has a relativelysmaller effect on the piston movement, since the piston stroke isconsiderably larger, corresponding to the mass ratio, than the swingingpath of the housing. On the other hand, the piston stroke If, namely, inthe case of steady-state operation of the engine, the initial pressurein the compression spaces is constant, then the piston stroke will begreater the more the frequency increases. This in turn makes automaticcontrol of such a piston swinging engine diflicult.

The present invention proposes effecting the control of the working airby a freely moving slide valve which is guided in a borehole lying inthe axial direction of the piston. The feeding of the working air can beeffected from the connecting connection connected to the housing throughan annular space in the housing or on the periphso developed that theworking air is conducted through an annular groove and correspondingradial bores, de-

pending on the position of the slide, to one side or the other of theworking surface of the swinging piston, depending on the position of theslide.

When the elastic intercepting of the piston in its end positions iseffected by air buffers, the working surfaces of this piston areordinarily made annular shape and arranged on both sides of a diskshaped step in the center of the piston. Since the slide valve is alsoax'ially approximately in the center of the piston, the

air is in this way introduced over the shortest path into the oneoperating space and discharged from the other. The leading away of thespent air from the one side is effected in this connection by thecentral opening of the slide valve.

In order to avoid unnecessary stresses, it is advisable to intercept thecontrol slide, in a manner similar to the piston in its two endpositions elastically, for instance by rubber buffers or in a similarmanner.

In connection with the development described, the acceleration of thepiston at the commencement of its movement is the greatest. It decreaseswith increasing speed of the piston, reaching a value of zero,approximately in the central position. Upon movement beyond the centralposition, a delay takes place since the air buifer which intercepts thepiston enters into action. Since the slide valve is guided in a freelyswinging manner in the direction of swing in the engine, it imparts theacceleration thereof at the beginning of the piston stroke untilreaching the central position. From then on, the slide valve swingsautomatically with respect to the swinging piston and therebyexperiences the relative displacement with respect to the swingingpiston.

which in accordance with the invention is used to control the workingair, advisedly the fresh air as well as the spent air.

Since the piston is arranged in a freely swinging manner in its housing,there is no preferred position of the piston with respect to the housingin which the former comes to a stop upon the shutting off of the workingair. This must be taken into consideration also in connection with thedevelopment of the slide valve.

In order to effect with certainty, at every possible position of thepiston, a control of the air corresponding to this piston position, itis provided in accordance with the invention that the slide valve ismoved with a supplementary device which brings it, upon the shutting offof the air, into its one dead center position and upon reconnection ofthe drive guides the slide valve, advisedly with reduced speed, onceover its entire control path so that it definitely also passes throughthe control position corresponding to the position of the piston, in itsinstantaneous position with respect to the housing or engine cylinder,and the piston is fed working air on one side or the other.

As a suitable device for the obtaining of the said displacement of thecontrol piston upon the shutting off of the working air and uponreconnection thereof, there can be used for instance a piston which ispredominantly in communication with the compressed air line and which isstruck on the opposite side by a force of such magnitude that when thecompressed air is connected, it is forced into its one end positionwhile when the air is disconnected it is forced by the counterforce intoits other end position. This auxiliary piston can for instance bedeveloped as a differential piston, in which case the necessarycounterforce is achieved by the fact that the smaller piston surface onthe rear side of the piston is struck by the same fresh air via anon-return valve.

This auxiliary piston can for instance be detachably connected via acoupling rod with the slide valve in the manner that the coupling of thetwo parts is effected when the auxiliary control piston, as well as theslide valve is moved back upon the shutting off of the drive from onedead-center position into the opposite end position. Upon the connectingof the working air which only acts in throttled state on the auxiliarypiston, the control slide is pushed over into its opposite end position.Since in this connection the auxiliary piston moves over a larger paththan the control piston can move over, the resilient coupling betweenthe coupling rod and the 3 control slide is positively loosened and thecontrol slide is now left to itself.

One embodiment by wayof example of the invention is shown in the drawingin which: I a

Fig. 1 is a longitudinal section through the engine;

Fig. 2 is a cross-section along the line 22 of Fig. 1; and

Fig. 3 is a cross-section along the line 33 of Fig. l.

A piston engine according to the invention includes an engine cylinderhaving an engine piston slideably mounted therein so as to form apiston-cylinder arrangement, and means are disposed on each side of thepiston so as to provide a working space within the cylinder on each sideof the piston. Further, means are provided for communicating first oneand then the other of the working spaces with a source of relativelyhigh pressure and simultaneously, respectively communicating said otherspace and then said one space with a source of relatively low pressurefor reciprocating the piston relative to the cylinder. This means forreciprocating the piston includes a tubular axially extended spacewithin the piston and a tubular slide valve slideably mounted in thetubular space for axial movement therein in response to reciprocation ofthe piston. During this movement, the slide valve reciprocates *betweena first position and a second position. The slide valve has an outerperipheral annular space disposed intermediate the ends thereof andwithin said tubular space of the piston. This outer peripheral annularspace is hermetically sealed from the balance of the tubular space bythe sliding engagement of the ends of the slide valve and the tubularspace. Means are provided for communicating the tubular space with afirst pressure source and means are provided for communicating theperipherial annular space with a second pressure source. Additionally,radially extending passageways communicate the tubular space with theengine working space so as to communicate one working space with thefirst pressure source and the other working space with the secondpressure source, with the slide valve in its first position andreversing the communication of the working spaces with the first andsecond pressure sources with the slide valve in its second position. Theslide valve is freely slideable in the tubular space within the piston,and hence, in response to reciprocation of the piston, the slide valveis shuttled between the first and second positions and provides controlvalve action for the engine.

The construction, according to the invention, is advantageously employedin combination with piston engine provided with means for pneumaticallyarresting each working stroke "of the piston. Conveniently,pneumatically arresting of'the working strokes is provided for byincluding at each axially disposed end of the engine a cylinderextension which slideably receives a piston extension developed so as toform the engine working spaces as annular working spaces. Means, such asend walls are arranged at the outwardly disposed end of each cylinderextension and the length of the cylinder extension exceeds the throw ofthe piston extension. Means are provided for maintaining a body of gasin the cylinder extension, and thus arrest reciprocation of the piston.The piston extensions alternately compress and expand gas within thecylinder extension and provide the desired pneumatic arresting action.

According to the invention, there is provided a slide valve positionerfor suitably positioning the slide valve with respect to the piston tocoordinate the valve and piston upon starting the engine. The positionerincludes a hook which is moveable axially within the tubular spacedisposedin the piston, and a catch which is secured to the slide valve.Means are provided which are responsive to disconnection of the enginefrom the source of relatively high pressure employed to motivate theengine, and efiective to move the hook axially in the tubular space,relative to the slide valve and engage the catch of the slide valve.Further, means are provided which are responsive to connection of theengine to the source of relatively high pressure, and this means iseffective to move the slide valve by the hook relative to the piston tocoordinate the position of the piston and slide valve and aftereffecting the coordination, to disengage the hook and catch and therebyrelease the slide valve from the hook.

Conveniently, the slide valve positioning means can include adiiferential piston axially mounted in the engine piston for slidingmovement therein, and the annular chamber of the differential piston andthe outer side of the large piston of the differential piston arecommunicated with a high pressure source and the outer side of thesmaller piston of the differential piston is communicated with a lowpressure source. The annular chamber is communicated with the highpressure source through a check valve which permits flow into theannular chamber. The differential piston is arranged to reciprocate inthe engine piston upon the engine being started and stopped so that thedifferential piston completes a stroke in one direction upon thestarting of the engine and completes a stroke in the other directionupon the stopping of the engine. The hook is secured to the difierentialpiston for movement axially through the tubular space upon movement ofthe differential piston and the catch is secured to the slide valve forengagement by the hook when the differential piston moves in the enginepiston upon stopping of the engine, and the catch is also arranged formoving the slide valve with the differential piston upon starting theengine. The stroke of the differential piston is coordinated with thestroke of the slide valve between the first and second position of theslide valve. Suitable means are provided for disengaging the hook andcatch after coordination of the slide valve and piston.

Referring to the drawing, the engine there shown comprises an enginecylinder 10 having slideably mounted therein an engine piston 11. Theengine cylinder is provided with cylinder extensions 51 and 52, whichin- Ielude respectively, cylinder extension end-walls, 53 and 54, andhave slideably mounted therein piston exten- I sions 55 and 56.

The piston annular disk 12 arranged approximately in the longitudinalcenter extends into the widened space 13 of the cylinder 10. In thisconnection, there result the two working spaces 14 and 15. Furthermore,the two piston discs 16 and 17 of piston extensions extend into thecompletely enclosed spaces 18 and 19 at the ends of the cylinder 10. Thespaces 18 and 19 are the butter spaces for the elastic interception ofthe swinging piston at the end of one or the other movement stroke. Thefeeding of the working air is effected through the connecting member 20which is arranged on the housing 10. Through this connecting member, theair passes through the outer annular channel 21 and the radial boreholes22 into the annular space 23 which, in the embodiment shownschematically, is reached by an annular groove 23 in the piston 11. Thelength of this annular groove 23 corresponds to the motion stroke of thepiston 11 relative to the housing 10. The compressed air thereforepasses continuously from space 23 through the longitudinal channels 24into the annular space 25 which surrounds the axial control borehole ofthe piston 11 in its center. From the annular space 23, however,compressed air at the same time continuously passes via the channel 26and the non-return valve 27 into the buffer space 19'. The buffer space18 is filled through the axial conduit 28 branching ofl? from theannular space 25 and via the non-return valve 29. The leading away ofthe spent air is effected through the axial borehole 30 of the piston 11and through the radial boreholes 31, the annular chamber 32 and theexhaust openings 33. In the drawing the parts are shown in such aposition that the working space 14 communicates with the exhaust 33. Atthe same time, due to, the annular control slide 34 whichis provided onits periphery with a circumferential groove 35, the working space 15 isconnected by radial channels and the annular space 35 of the controlslide 34 with the chamber 25 which is continuously in communication withthe fresh air connection 20.

The control slide 34 is displaceable in its longitudinal direction withrespect to the reciprocating piston 11. The path of displacement islimited by two stops. The blow is softened in this connection bybuffering means 36 which can be rubber bumpers. 1 The displacement ofthe slide 34 at the beginning of its motion stroke takes placepositively upon the displacement of the swinging piston 11 since theslide 34, first of all, for instance in the piston shown in Fig. 1,rests via its right end edge against thereciprocating piston. When,however, the swinging piston 11 is delayed after movement beyond itscentral position, the control slide 34 moves away from the swingingpiston 11 and carries out, under the influence of the kinetic energyinherent in it, a relative movement with respect to the piston 11.

I By this relative movement, there is then at the same time obtained thedesired reversal of the driving medium. The annular space 35 of thecontrol slide 34 then connects the fresh air chamber 25 with the workingspace 14 of the piston. The piston is therefore struck in oppositedirection. At the same time the second working space 15 is now connectedvia the central opening 37 of the control slide 34 with the exhaustchannel 30. By this switching of the driving medium, the desiredreversal of the swinging piston 11 is thus positively produced. Upon thenext movement stroke of the piston 11, a new reversal of the controlpiston 34 then again automatically takes place with the eflfect that theengine which is once in operation remains operating as long as thecompressed air is not shut off. It is important that the switching takeplace independently of the position assumed by the swinging pistion 11in the swinging hous ing 10.

' In order to make possible the starting of the engine in any positionof the swinging piston 11 in the swinging housing 10, there is providedan auxiliary device which draws the control slide 34 upon the shuttingall of the working air always into the position shown diagramniaticallyin Fig. l, the auxiliary device being connected with the control slide.If the compressed air feed is again opened, it slowly displaces thecontrol slide 34 over its entire movement stroke up to its other endposition, where the control slide 34 is positively disconnected from theauxiliary device. The control slide in this connection passes throughall possible control positions and therefore also the position in whichthe compressed air is so controlled thatthe piston 11 in the positionwhich it has just assumed is acted upon by compressed air, either on oneside or on the other side, and therefore is displaced in one directionor the other. This first acceleration of piston 11, as alreadymentioned, results however in an automatic reversal of the controlflldeML;

In the embodiment shown in the drawing, the auxiliary device consists ofthe stepped piston 38, the larger piston disk 39 of which moves in abore 40 of the piston 11, while the smaller disc 41 moves in thecylinder 42 of small diameter. The cylinder space 40 communicates viathe narrow bore 43 with the 'fresh air channel 26. A non-return valve 44leads a part of this compressed air into the annular chamber 45 betweenthe two piston disks 39 and 41. The differential piston 38 bears in itsaxial extension a rod 46 having a reinforced head 47. This rod passesthrough the ring 48 borne by the slide 34, on which ring there arearranged the springs 49 which surround the rod-head 47 when the partsassume a corresponding position with respect to each other.

In Fig. 1 of the drawing, the control slide 34, as well as the auxiliarypiston 38, is shown in the position which of the parts shown, the partsimmediately act on the working space and thus displace the swingingpiston 12 toward the left. Furthermore, however, the larger pistonsurface 39 of the auxiliary piston 38 is acted upon and the controlslide 34 moved positively toward the left into its end position.Sincethe auxiliary piston 38 can move a larger distance toward the left,when the lefthand end position of the'control slide 34 is reached, therod head 47 is forced out of the spring 49. The working space 14 is nowacted upon and upon further operation, the control slide 34 can freelyfollow the acceleration forces of the piston 11, while the auxiliarypiston 38 remains in its left end position. In any event the auxiliarydevice sees to it that the control slide, upon the connecting of theworking air, is automatically displaced once over its entire path ofmovement so that it passes through all possible control positions.

What is claimed is:

l. A piston engine comprising an engine cylinder hav- V ing an enginepiston slidably mounted therein forming a piston-cylinder arrangement,means disposed on each side of the piston providing a working spacewithin the cylinder on each side of the piston, operating means forcommunicating first one and then the other of said working spaces with asource of relatively high pressure and simultaneously respectivelycommunicating said other space and then said one space with a source ofrelatively low pressure for reciprocating the piston relative to thecylinder, said operating means including means defining a tubularaxially extending space within the piston, and a tubular slide valveslidably mounted in said space for axial movement therein in response toreciprocation of the piston between a first position and a secondposition, said slide valve having means defining an outer peripheralannular space intermediate the ends thereof and disposed within saidtubular space and hermetically sealed from the balance of said tubularspace, means for communicating said tubular space with a first pressuresource, means for communicating said peripheral annular space with asecond pressure source, mean defining radially extending passagewayscommunicating said tubular space with the working spaces forcommunicating one working space with said first pressure source and theother working space with said second pressure source with the slidevalve in said first position and reversing the communication of theworking spaces with the first and second pressure sources with the valvein said second position, whereby in response to reciprocation of thepiston the slide valve is shuttled between said first and secondpositions and provides control valve action for the" engine.

2. A piston engine according to claim 1 including means for elasticallyarresting the movement of the slide valve into the first position andthe second position.

3. A piston engine according to claim 1, wherein said working space isan annular working space.

4. A piston engine according to claim 1 including means forpneumatically arresting each working stroke of the engine piston.

5. A piston engine according to claim 1 including at each axiallydisposed end of the engine a cylinder extension slidably receiving apiston extension, means closing the outwardly disposed end of thecylinder extensions, the length of said cylinder extensions exceedingthe throw of said piston extensions, and means for maintaining a body ofgas in said cylinder extensions whereby each working stroke of theengine piston can be pneumatically arrested.

6. A piston engine according to claim 1 including a slide valvepositioner for suitably positioning the slide valve with respect to. thepiston to coordinate the valve and piston upon starting the. engine,said positionerineluding a hook movable within said tubular. space andacatch secured to said slidervalve, meansrresponsive to disconnectionfrom theengine of said source of: relatively highpressureandeffective tomove the hook axially in said tubular spacerelative to the slideyalveand en.- gage said catch and means responsive to: connection of theengine to said. source of relatively high pressure. and effective tomove'the slide valve by said hook relative to the piston to coordinatethe position of the piston and slide valve and thereafter; disengage thehook. and catch and thereby release the slide valve.w

7. A piston engine according to claim 1 including. a slide valvepositioner' for suitably positioning the slide valvewith respect.totheipiston to coordinate the valve and piston upon starting theengine, said. positioner including a differential piston axially mountedin saidv engine piston for sliding movement therein, the annular chamberof the differential piston and the outer side of the large piston of thedifferential piston being communicated with a high pressures source andthe outer side of the smaller piston of; the differential. piston beingcommunicated with a low pressure source, said annular chamber beingcommunicated. with said high pressure source through a check valvepermitting flow into the: annular chamber, sm'd differential pistonbeing arranged to reciprocate in the engine piston upon the engine beingstarted and stopped completing a stroke in one direction upon startingofthe engine and completing a stroke in the other direction upon stoppingof the engine, a. hook secured to said differential piston for movement.axially through the tubular space upon movement of the differentialpiston, a catch secured to said slide valve for engagement by said hookwhen the differential piston. moves in the piston upon stopping theengine and for. moving the slide valve with the differential piston uponstarting the engine, the stroke of the differential piston being coordimated with the stroke of the slide valve between said first and secondpositions thereof to coordinate the position of the slide valve and thepiston by operation of the difierens tial piston upon starting theengine, and means for'dis-' engaging the hook and catch aftercoordination of the slide valve and piston.

8. A piston engine according to claim 1, said means for communicatingthe tubular space with a first pressure source and the peripheralannular space with a second pressure source each comprising a groovedisposed in the outer surface of the piston of axial length at leastequal to the stroke of the piston, means defining an opening in theengine cylinder communicating the groove and the outside of the cylinderthroughout the stroke of the engine piston, and a radially extendingpassageway in the cylinder communicating with the groove.

9. A piston engine according to clairn- 1, including means forpneumatically arresting each working stroke of the engine piston, andfurther including a slide valve positioner for suitably positioning theslide valve with:

respect to the. piston to coordinate the valve ,andipiston:uponzstarting theengine, saidpositioner including audit; ferentialpistonaxially mounted in saidiengine-pi'ston for sliding movement therein,vthe annular chamber of the differential piston and the outer side of thelarge piston of'the differential piston being communicated with a highpressure source and the outer side of the smaller piston lofthedifferential piston being communicated with a low pressure source, saidannular chamber being cornmunicated :with said high pressure sourcethrough. a check valve permitting flow into the annular chamber; saiddifferential piston being arranged to reciprocate in the engine pistonupon the engine being started and stopped completing a stroke in onedirection upon starting of theengine and completing a stroke in theother direction upon stopping of the engine, a hook secured to saiddifferential piston for movement axially through the tubular spaceuponmovement of the differential piston, a catch secured to said slide valvefor engagement by said hook when the dilferential piston moves in thepiston upon stopping the engine and for moving the slide valve with the"differential piston upon starting the engine, the stroke of thedifferential piston being coordinated with the stroke of the slide valvebetween said first and second positions thereof to coordinate theposition of the slide valve and the piston by operation of thedifferential piston upon starting'the engine, and means for disengagingthe hook and catch after coordination of the slide valve and piston,said means for communicating the tubular space with a first pressuresource and the peripheral annularspace with a second pressure sourceeach comprising a groove disposed in the outer surface of the piston ofaxial length at least equal to the stroke of the piston, means definingan opening in the engine cylinder communicating the groove and theoutside of the cylinder throughout the stroke of the engine piston,- anda radially extending passageway in the. cylinder communication With thegroove, means for elastically arresting the movement, of the slide valveinto the first position and the second position.

10. A piston engine according to claim 9, said outer peripheral annularspace of the slide valve being communicated with the source ofrelatively high pressure and the portion of said tubular spacehermetically sealed from the outer peripheral annular space being cot-nmunicated with the source of relatively low pressure.

References Cited inthe file of this'patent UNITED STATES PATENTS GreatBritain Dec. 15,1954

